I understand what you're saying, its somewhat selfish, but such is the way of the world. As the elite athlete, he gets all the choices. He has the opportunity to delay his choice until "the last minute" and lesser athletes have to wait in the wings.
Something I have observed, both as parent, and a follower of sports, is that many young guys around this age are somewhat impatient. Not a criticism, just an observation. Guys who were offered the opportunity to get into AFL a year early (when CG and GWS joined) leapt at the chance, rather than wait for the draft.
Partially, I think that Basketball has itself to blame.
It has become the "accepted" pathway, that if you are halfway decent, you try to get a US college scholarship. Some are far too desperate for this opportunity, they end up either having to spend time at a US high-school, or Junior College, or some redshirt, get a degree in "general studies" and return home broke at 22~24. If such a kid had a shot at being drafted to AFL at 18, he'd be mad not to take it.
I don't know what the alternative is to the college period, and I'm not saying its not a great experience, but if a players is actually good enough to have a choice between 4 years at college, and 4 years in the AFL, then for most its a no brainer.
As others have mentioned, its also about size.
Speed, endurance, and coordination are far more important in the AFL. 195cm is still considered Tall in AFL and would likely see you play as a Key Position Player. Guys under 180cm can still get a gig.